In methods for carrying out the maintenance of systems (parts of products or complex products) it is of particular interest to be able to reduce unexpected faults by monitoring certain parameters indicating the state of the system.
According to the prior art, in the aeronautical sector the presence of damage or defects in a mechanical structure of an aircraft, such as a metal or composite structure, for example fuselage or wing structure, is diagnosed indirectly by means of a historical reconstruction of events, including events which have resulted in damage due to an accidental impact during production (impact of a tool) or while in service (impact due to hail or foreign objects), and loads withstood by the structure, or by means of estimate of the fatigue withstood by the structure, based on the knowledge of its mechanical strength properties in response to the stresses which typically occur in service conditions. In particular, in the case of composite structures, accidental impacts produce effects which are not very visible externally, but may cause considerable damage inside the structure (for example, delamination).
This technique, however, is laborious and imprecise, because it does not reflect in real time the changes and the physical and mechanical conditions of the monitored structure.
A method for predicting the behaviour of a structure subject to loads was developed by the same Applicant and described in the European patent application EP 2,281,224 A1. The method comprises the provision of a mathematical model of the structure, detection of the state (deformation) of the structure in a plurality of primary points and in a plurality of additional points, determination of the loads acting on the structure and associated with the state detected in the primary points on the basis of the aforementioned mathematical model, estimation, using the loads determined, of the state of the structure in the additional points, and comparison between the state of the structure estimated and that detected in the additional points, so that an intact state of the structure is determined if the estimated and detected values of the state parameter match, or a defective state of the structure if these values differ.